Drop dependency on m4

m4 was hugely popular in the past, because autotools, automake, flex, bison and
many other things used it. But nowadays it much less popular, and might not even
be installed in the buildroot. (m4 is small, so it doesn't make a big difference.)

(FWIW, Fedora dropped make from the buildroot now,
https://fedoraproject.org/wiki/Changes/Remove_make_from_BuildRoot. I think it's
reasonable to assume that m4 will be dropped at some point too.)

The main reason to drop m4 is that the syntax is not very nice, and we should
minimize the number of different syntaxes that we use. We still have two
(configure_file() with @FOO@ and jinja2 templates with {{foo}} and the
pythonesque conditional expressions), but at least we don't need m4 (with
m4_dnl and `quotes').

.mkosi/mkosi.arch

@@ -35,7 +35,6 @@ BuildPackages=
         libxkbcommon
         libxslt
         lz4
-        m4
         meson
         pam
         pkgconfig

.mkosi/mkosi.debian

@@ -46,7 +46,6 @@ BuildPackages=
         libtss2-dev
         libxkbcommon-dev
         libzstd-dev
-        m4
         meson
         pkg-config
         python3

.mkosi/mkosi.fedora

@@ -45,7 +45,6 @@ BuildPackages=
         libzstd-devel
         lz4
         lz4-devel
-        m4
         meson
         ninja-build
         openssl-devel

.mkosi/mkosi.opensuse

@@ -30,7 +30,6 @@ BuildPackages=
         libseccomp-devel
         libselinux-devel
         libxslt-tools
-        m4
         meson
         pam-devel
         pciutils-devel

.mkosi/mkosi.ubuntu

@@ -49,7 +49,6 @@ BuildPackages=
         libxkbcommon-dev
         libxtables-dev
         libzstd-dev
-        m4
         meson
         pkg-config
         python3

README

@@ -195,7 +195,7 @@ REQUIREMENTS:
         python >= 3.5
         meson >= 0.46 (>= 0.49 is required to build position-independent executables)
         ninja
-        gcc, awk, sed, grep, m4, and similar tools
+        gcc, awk, sed, grep, and similar tools
         clang >= 10.0, llvm >= 10.0 (optional, required to build BPF programs
                 from source code in C)
 

meson.build

@@ -606,7 +606,6 @@ echo = find_program('echo')
 test = find_program('test')
 sed = find_program('sed')
 awk = find_program('awk')
-m4 = find_program('m4')
 stat = find_program('stat')
 ln = find_program('ln')
 git = find_program('git', required : false)
@@ -1650,7 +1649,6 @@ generate_gperfs = find_program('tools/generate-gperfs.py')
 make_autosuspend_rules_py = find_program('tools/make-autosuspend-rules.py')
 make_directive_index_py = find_program('tools/make-directive-index.py')
 make_man_index_py = find_program('tools/make-man-index.py')
-meson_apply_m4 = find_program('tools/meson-apply-m4.sh')
 meson_render_jinja2 = find_program('tools/meson-render-jinja2.py')
 update_dbus_docs_py = find_program('tools/update-dbus-docs.py')
 update_hwdb_sh = find_program('tools/update-hwdb.sh')

test/TEST-06-SELINUX/test.sh

@@ -48,7 +48,7 @@ test_append_files() {
         cp systemd_test.fc "$workspace/systemd-test-module"
         dracut_install -o sesearch
         dracut_install runcon
-        dracut_install checkmodule semodule semodule_package m4 make load_policy sefcontext_compile
+        dracut_install checkmodule semodule semodule_package make load_policy sefcontext_compile
         dracut_install -o /usr/libexec/selinux/hll/pp # Fedora/RHEL/...
         dracut_install -o /usr/lib/selinux/hll/pp     # Debian/Ubuntu/...
     )

test/mkosi.default.networkd-test

@@ -52,7 +52,6 @@ BuildPackages=
         libxslt
         lz4
         lz4-devel
-        m4
         meson
         ninja-build
         pam-devel

tools/meson-apply-m4.sh

@@ -1,21 +0,0 @@
-#!/usr/bin/env bash
-# SPDX-License-Identifier: LGPL-2.1-or-later
-set -eu
-
-CONFIG="${1:?Missing path to config.h}"
-TARGET="${2:?Missing target m4 file}"
-
-if [ ! -f "$CONFIG" ]; then
-    echo "$CONFIG not found."
-    exit 2
-fi
-
-if [ ! -f "$TARGET" ]; then
-    echo "$TARGET not found."
-    exit 3
-fi
-
-DEFINES=()
-mapfile -t DEFINES < <(awk '$1 == "#define" && $3 == "1" { printf "-D%s\n", $2 }' "$CONFIG")
-
-m4 -P "${DEFINES[@]}" "$TARGET"